1. Field of the Invention
The present invention relates to a method for processing a large number of fish eggs, in particular to an automated method for processing fertilized fish eggs. The invention can be employed for production method for producing genetically recombinant proteins and so on from fertilized fish eggs by gene injection. Furthermore, the invention can be employed to produce materials by means of using fertilized fish eggs.
2. Description of the Related Art
A method to produce specific protein is known by injecting gene material to the fertilized egg of the fish. This protein-producing method may have high productivity, because the specific fish such as the zebra fish lay eggs approximately every day.
The gene material must be injected into each fish eggs before dividing of the fertilized fish egg is started. However, a very large number of the fish eggs employed for the gene-injection is very small. For example, the eggs of the zebra fish have a diameter of about 1 mm. It is not easy to deal very large number of small fish eggs within a short time. Moreover, the injection apparatus for injecting the gene material into the small fish egg is expensive, because precision control is required for an injection needle to inject the gene material into the very small fish egg.
It is known that zebra fish lays eggs by means of lighting. Japan Unexamined Patent Publication No. 2001-120,110 proposes a rectangular-shaped water tank having square-shape in the horizontal direction. Water supplied to an upper portion of the water tank is drained out from a drainage pipe established in the bottom of the water tank. A square-shaped upper half portion of the water tank consists of four pieces of perpendicular wall plates. A reverse-pyramid-shaped lower half portion of the water tank consists of four pieces of slope wall plates. Each slope wall is slanted diagonally.
However, it is considered that the fish eggs is caught easily at corners between two slope wall plates of the reverse-pyramid-shaped lower half portion of the water tank. It is difficult to separate the caught fish eggs from the corners, because a fish-separating net is disposed between the upper portion and the lower portion of the water tank. The fish eggs staying for a long time at the corners deteriorate the quality of the water.
Japan Patent No. 3,769,680 illustrates a water tank having a cylinder-shaped upper portion and a cone-shaped lower portion. A pair of water-supplying pipes is disposed horizontally at the cylinder-shaped portion. A pair of drainage pipes is disposed at the cylinder-shaped upper portion. These pipes makes rotating water stream in the water tank. The rotating water stream rises upwardly.
U.S. Pat. No. 4,798,168 illustrates a water tank having a cylinder-shaped upper portion and a cone-shaped lower portion. A pair of water-supplying pipes is disposed horizontally at the cylinder-shaped upper portion of a water tank. A drainage pipe is connected to a bottom hole disposed at a top of the cone-shaped lower portion of the water tank. These pipes makes rotating water stream in the water tank. The rotating water stream descends downwardly. However, these water tanks described in the patent documents 2-3 needs a large horizontal space.